This is a multi-center, randomized, double-blind, parallel-group trial. After a 2-week run-in period, eligible patients will be, based on the randomization codes kept in sealed envelopes, randomly assigned to receive usual care (mucolytics and/or chest physiotherapy) plus oxygen inahaltion (1 hr daily for 12 consecutive months) or hydrogen inhalation (1 hr daily for 12 consecutive months) provided by the sponsor. At 3 months after the end-of-treatment, a follow-up visit will be scheduled for all patients.